Many others on this board have gone through full pregnancies successfully (and several). Think about it this way - during pregnancy, there's info that your immune system will relax, hopefully creating less need for medication (hah...maybe have 18-20 kids?).
Also, nature/nurture. Since you know a child is predisposed to AS, you'd make sure to create the optimal diet - lots of vitamin D. Low grains, tons of veggies, quality high density meats.
I'd say let your husband read about AS, but then remember that no case is classic. Some folks go into remission - some get worse - some stay the same. There's really no way to know, but you can always do 100% to take care of yourself.
